Conventionally, vehicle locking differentials have been provided for co-axial arrangements of two drivers, two axle couplers, and a locking mechanism subject to differential rotational forces provided by respective left and right axles, which provide a locking or unlocking effect by such members.
FIG. 1 illustrates an exploded view of a locking differential. As illustrated in FIG. 1, a splined inner end (teeth) of axle 120 engages mating splines (teeth) in an axle coupler 122. In the shown embodiment, the axle 120 is retained in position by a C-clip 124. It is noted that the axle retention mechanism may be realized by bearings adjacent to wheel ends of the axles or other means such as a snap ring.
The axle coupler 122 have a plurality of drive teeth 126 on the face thereof which may mate with corresponding teeth on faces 128 of drivers 130, depending upon the axial position of the drivers. The drivers 130, in turn, have saddle-like depressions 132 on the opposite faces thereof for loosely surrounding a pinion pin 134 driven by the differential case.
The driver 130 has a spring 136 in angled blind holes in the driver 130, the spring 136 acting on pin 134 to both elastically encourage the drivers 130 to a position having the pin 134 aligned with the center of the saddle-like depressions 132, and to elastically encourage the drivers 130 axially outward away from the pin 134 into engagement with the axle couplers 122.
Spacers 138, together with any shims or thrust washers that may be required (not shown), establish and retain the axle couplers 122 at the desired separation from pin 134.
It is noted that the C-clip 124, when the differential is assembled, is located in a recess or cavity 150 of the spacer 138. In other words, the retention mechanism (C-clip 124) is positioned between the axle coupler 122 and the driver 130.
Finally, pins 140 on the drivers 130 fit within slots 142 on the opposing face of the opposite driver and function to control the angular displacement of the drivers 130 relative to each other.
In the final assembly, the springs 136 encourage the toothed face of the drivers 130 into engagement with the toothed face of axle couplers 122, and there is sufficient clearance between the saddle-like regions 132 and pin 134 in the final assembly for either driver 130 to move toward the pin 134 sufficiently to allow the teeth of a driver 130 to ride over the teeth of the associated axle coupler 122.
The operation of the differential of FIG. 1 may be explained as follows. With the teeth of the corresponding driver and axle coupler pairs engaged, the differential housing may rotate, carrying the pin from contact with one side of the saddle to the other, a displacement of (depending on the size of the design) 4 to 7 degrees. This free travel, or backlash, is essential for correct positioning of the differential components during the transition from driving to coasting and vice versa.
The drivers are retained with respect to each other by the pins 134 and mating slots 142 for a total rotation, one relative to the other, approximately 1.5 degrees or less than one-half the total backlash described previously. When the pin 134 engages the saddle-like depressions 132 on either driver, the force of the contact, by design of the saddles 132, will be angled outward from the plane of the respective driver and will overcome the component of the reaction force acting opposite created by the inclined edges on the mating teeth on the drivers 130 and axle couplers 122.
For example, saddle angles ranging from 30 to 40 degrees are typically used and create outward axial forces that exceed the inward axial forces created by typical 20 to 25 degree inclines of the coupler and driver mating teeth that would otherwise work to separate the driver from the coupler.
Using the foregoing parameters, consider first the vehicle at rest. Assume the two drivers 130 each engage with the respective axle coupler 122, and for specificity in the starting condition, that the pin 134 is centered in the saddle-like depressions 132 in the drivers 130. With the vehicle in gear and engine driving, the pin 134 begins to rotate about the axis of the axle, through the backlash present and compressing against springs 136 to contact the edges of the saddle-shaped depressions 132 in the drivers, and then on further rotation, to force the drivers 130 and axle couplers 122, and thus the axles, into rotation.
Since the contact angle between the pin 134 and the saddle-shaped depressions 132 exceeds the angle of the edge of the teeth on the axle couplers 122 and drivers 130, the force between the pin 134 and the drivers 130 forcing the same into contact against the axle couplers 122 will exceed the force between the inclined edges of the teeth on the drivers 130 and axle couplers 122 otherwise tending to force the drivers 130 back toward pin 134, so that the drivers 130 and axle couplers 122 will remain in positive engagement, regardless of the torque applied to the differential.
If the vehicle now proceeds to drive around a curve, the wheel on the outside of the curve, and thus the axle coupler 122 associated with that wheel, will tend to rotate faster than the axle coupler 122 associated with the inside wheel.
Assuming power is still being applied, this causes the driver 130 associated with the outside wheel to begin “gaining” with respect to pinion shaft 134, the driver 130 rotating forward to a position wherein the saddle-like depressions 132 thereon are no longer in contact with pin 134.
At this point, pins 140 and mating depressions 142 prevent the further relative rotation of the two drivers 130 but allow coaxial translation. Further gaining of the outside wheel continues to rotate the outside axle coupler 122 at a speed higher than the other differential components. Now, however, the teeth on the driver 130 associated with the outside wheel are free to climb the inclined planes of the teeth on the driver 130 and axle coupler 122, with the driver 130 moving toward the pin 134 against the resistance of the associated springs 136 to allow the teeth of the respective driver 130 to slide over the teeth of the respective axle coupler 122, repeatedly as required so long as the difference in wheel rotation speeds exist.
If, when in a curve, the vehicle engine is throttled back to coast and use the engine as a braking or vehicle slowing device, the same basic interaction of parts described above will occur substantially in reverse, now however with the driver and axle coupler associated with the outer wheel of the curve being engaged, and the driver associated with the inner wheel of the curve climbing over the teeth on the associated axle coupler as required to allow the inner wheel on the curve to turn slower than the outer wheel.
Similarly, in backing around a curve such as backing out of a parking place, the inner wheel will be the drive wheel, as in powering forward, whereas use of the engine to retard the motion of the vehicle when backing will engage the wheel on the outer side of the turn engaged. However in any event, when power is applied while turning to the point that traction is lost by the drive (inside) wheel, the pin 134 will catch up to and forcibly engage the appropriate side of the saddle-shaped depression 132 on the outside wheel driver 130, forcing both drivers 130 into engagement with their associated axle couplers 122 to force rotation of both axles in unison.
When utilizing an axle retention mechanism, it is desirable to provide a mechanism that enables the axle retention mechanism to securely engage an axle and the axle coupler.
Moreover, it is desirable, when utilizing an axle retention mechanism, to provide mechanism that enables the axle retention mechanism to securely engage an axle and the axle coupler without interfering with the engagement of the drive teeth of the axle coupler and the drive teeth of the driver.
Furthermore, it is desirable, when utilizing an axle retention mechanism, to provide a mechanism, located within the central aperture of the axle coupler, that enables the axle retention mechanism to securely engage an axle and the axle coupler without interfering with the engagement of the drive teeth of the axle coupler and the drive teeth of the driver.